Rotary face seals typically comprise two contacting rings where one ring rotates with respect to the other. The seal is made between the opposing faces of the two contacting rings. Force is provided in some manner in order to maintain sealing contact between the rings.
Such rotary face seals are used for numerous commercial purposes. A relatively new application for rotary face seals has been for use in compact and/or rapid cycle pressure swing adsorption (PSA) devices. For instance, U.S. reissue Pat. No. RE38,493, incorporated herein by reference, discloses such devices. Therein, rotary face seals form part of pressure balanced rotary distributor valves that are used to open and close the feed and product ends of the adsorbent beds employed in a PSA device. Various rotary pressure swing adsorption devices also are disclosed in U.S. Provisional Application Nos. 60/886,484 and 60/886,486, both of which are incorporated herein by reference. In addition, PCT application number PCT/CA2008/000148, titled “Gas Separation Device”, filed Jan. 23, 2008, discloses a rapid cycle pressure swing adsorption (RCPSA) device which also employs rotary face seals in rotary valves used at both the feed and product ends of the adsorbent beds therein. In the embodiments disclosed by this PCT application, the force used to maintain contact between the sealing surfaces can be provided by various gases as opposed to being provided by mechanical means (e.g. springs).
Problems associated with temperature gradients and thermal distortion in rotary face seals have been encountered in the prior art and some solutions have been proposed. For instance, U.S. Pat. No. 4,850,599 discloses a rotary mechanical face seal having a construction which keeps the sealing faces substantially parallel in spite of thermal distortion of the seal face members.
In many PSA applications (such as in separating hydrogen from refinery waste streams), the temperature variations experienced by the rotary valves in the PSA device can be significant. In addition, significant temperature gradients may also exist across the rotary valve and/or seal components. For these reasons, it is important that the rotary face seals in these devices be sufficiently stable against variations in temperature and against temperature gradients.